This invention relates to cabin pressure controllers.
In an aircraft cabin, ideal conditions for passenger comfort exist when cabin altitude is maintained at sea level and when cabin pressure rate of change is maintained at zero. However, these conditions can rarely be achieved. Therefore, a cabin pressure control system is required to the control cabin altitude and pressure rate in a manner that optimizes passenger comfort.
In a cabin pressure control system, the cabin is typically back-pressurized. At least one outflow valve regulates the rate of air flowing out of the cabin so as to control the pressure inside the cabin. A digital cabin pressure controller issues commands for opening or closing the outflow valve as required to control the cabin pressure. The commands are typically generated according to parameters such as isobaric cabin altitude, cabin pressure rate and pressure differential (i.e., the difference between cabin altitude and ambient pressure). A selector located in the cockpit permits the crew to select the parameters. Cabin altitude is supplied to the controller by a remote sensor, and ambient pressure is supplied by an airdata computer.
Conventional cabin pressure controllers are installed with a distributed approach. A primary controller, a backup controller, a manual controller, a selector and a display are all housed in separate boxes.